Research by Louise Stewart at the University of Western Australia shows that there may be a link between early in vitro fertilization and breast cancer later in life, thanks to the collection of data on 21,025 women between 20 and 40 between 1983 and 2002.

They kept tabs on the women—some of whom had fertility treatments and IVF, and some who had treatments without IVF— for 16 years, and discovered that women who began taking fertility drugs and went through IVF around the age of 24 had a 56% greater chance of eventually developing breast cancer compared to those who didn't do in vitro fertilization. (The final number is 1.7 versus 2%, which is a narrow enough margin that scientists and health professionals are arguing that it's negotiable and may not have anything to do with IVF).

Even Stewart says of the results: "I don't think it's a huge increased risk that you should worry or panic (about)."

Meanwhile, there was no increased risk found in women over 40 who had fertility treatments, either with or without IVF.